Maybe I buried the lead in my previous commentary about why the San Francisco 49ers need to begin rebuilding the secondary.

Much like a fifth-grade essay, I will put my main thought up front.

I am in full support of the 49ers drafting or signing a highly talented edge rusher.

There are 152 articles each day stating the 49ers' need for an edge rusher. I have no interest in finding new nouns and adjectives to describe why Nick Bosa should become a 49er.

Fortunately, general manager John Lynch and head coach Kyle Shanahan are not myopic and realize they have other position groups to build, including the interior offensive line.

Tackles Joe Staley and Mike McGlinchey are staying put as the offensive line's bookends. With tackle Garry Gilliam finally off the roster, it leaves three-year veteran Shon Coleman as the swing tackle. Coleman didn't play a down last year, but he must have put in 16 weeks of solid practice and scout team work to show that he's a better tackle than Gilliam.

Like the 2017 season, the 49ers' Achilles heel remains with the interior offensive linemen.

Center Weston Richburg injured his knee during Week 4 and had surgery on his knee and quadriceps about a month ago. The 49ers expect Richburg to join the team for the start of training camp.

Left guard Laken Tomlinson nearly played every snap in 2018 before suffering an MCL injury during the final game against the Los Angeles Rams. Tomlinson improved his pass blocking last season, allowing three fewer hits, five fewer hurries and eight fewer pressures than in 2017. However, his run blocking dropped by nearly five points. Tomlinson's biggest asset is his ability to stay healthy, but he's not a top guard. His overall offensive grade still hovers in the mid-60s. (Pro Football Focus)

Right guard Mike Person played better than Tomlinson but ranked second on the offensive line in allowed pressures with 34. He allowed seven hurries, the lowest of any 49er lineman. Person will be a free agent in a few weeks, but it would be in the team's best interest if Lynch brought him back for the 2019 season.

Back-up interior linemen Joshua Garnett and Erik Magnuson played sparingly in 2018. Garnett is a former Outland Trophy winner, but could not beat Person out for a starting role in training camp. I have to assume Lynch and Shanahan have seen enough from both Garnett and Magnuson. Both may stay on the roster during the offseason, but I do not expect either to make the final cut.

Lynch needs to make another significant investment in the offensive line, and he should look 353 miles south at Los Angeles Rams' left guard Rodger Saffold.

Saffold is 30 years old and was the tenth best guard in the NFL according to Pro Football Focus. Rams' head coach Sean McVay ran 21 percent of the ground game through Saffold. In fact, Saffold was responsible for 24 percent of the team's rush yardage, and 22 percent of the rushing touchdowns.

Saffold's learning curve is also small since the Rams and 49ers run a similar offense.

I watched three of Saffold's games – Week 4 against Minnesota, Week 7 against San Francisco and Week 11 against Kansas City. He played well against Minnesota and San Francisco but struggled against Kansas City defensive lineman Chris Jones.

I'm an offensive line junkie, so watching Saffold was like finally catching the dragon. He's fluid with his feet and hips, he's rarely over-extended and has the aggression of a caged wolverine.

The Vikings pre-snap alignment isn't anything complicated or exotic. Both linebackers are dancing around the gaps trying to get a lineman to reveal the protection or rattle quarterback Jared Goff.

At the snap, Vikings linebacker Eric Kendricks shot the B-gap to Saffold's left. The pick-up, follow-through and Saffold's finish against Kendricks' weak blitz was a joy to watch.

Kendricks took a looping turn to his right, which made me wonder if he thought he and the defensive end were supposed to execute a TEX stunt. Kendricks' mental error took him out of the play, but Saffold stuck with him for a bit longer.

The second Saffold gained control of Kendricks, someone in the Los Angeles Coliseum shouted: "Finish him!" Saffold responded and hurled Kendricks into the green grass.

McVay called a screenplay from a what Shanahan calls a Dos Right formation. The fly motion from wide receiver Robert Woods was added to draw defenders away from the area.

Goff's fake and the offensive line's 'confusion' held the Vikings defenders in place. The mental lapse allowed Saffold to break into the second level, ready to lead the way downfield for Gurley. Notice how Saffold was looking inside for a safety or rogue linebacker to flash, but also kept his body in position to continue downfield.

Saffold is what the 49ers have been missing from the guards: an ability to lead a block twenty yards from the line of scrimmage. Fans have seen this type of blocking from Staley and McGlinchey, but Shanahan has not been able to use his guards in this manner.

Saffold played one of his best games against the 49ers. According to Pro Football focus, McVay called seven runs in Safforld's direction, gaining 32 yards and two first downs. He allowed one hit, one hurry, and two pressures.

49er fans should recognize the zone blocking scheme the Rams used. The Rams offensive line moved to the right for a zone run. From the pre-snap look, it's clear running back Malcolm Brown was going to bend back inside because he only had to beat nose tackle Earl Mitchell.

Saffold got a piece of Mitchell with help from his tackle. 49er defensive lineman Solomon Thomas was unblocked, but his long way around the end removed him from making any real threat at the line of scrimmage.

Notice how Saffold set himself up to get to the second level. He knew he had help from his tackle and could let Mitchell go to be of further assistance to Brown.

That's Saffold highlighted in the yellow box. His left tackle finished off Mitchell and Saffold was able to keep Warner from taking down Brown at the line of scrimmage. Brown gained nine yards on the run.

Week 7: Rams vs. 49ers – First quarter: 3rd and 3 at the LA 39 (1:27)

I watched this pass blocking ten times, and was impressed at what Saffold did to neutralize 49ers' defensive lineman DeForest Buckner.

The 49ers were threatening both A-gaps, but the Rams' offensive line must have known it was a ruse. Not one offensive lineman looked inside at the snap, and both 49er linebackers dropped into coverage.

With no threat inside, Saffold got a great jump to his left, giving him a better position to take on Buckner. The Rams used six-man protection, with the left tackle, guard, and center moving to the left. Saffold had help inside from the center and running back if 49er defensive end Robert Blair looped back inside.

Saffold was able to push Buckner well outside the pocket, sticking with the block until he was 13 yards from the original line of scrimmage.

I have no doubt both Tomlinson and Person accomplished a similar feat during the season, but not with the consistency and ease that Saffold did for the Rams.

Chiefs' defensive lineman Chris Jones gave Saffold fits all night, and I noticed Saffold in a weak position almost immediately after the snap. Against the Chiefs, Saffold allowed one sack, two hits, two hurries, and five pressures. Pro Football Focus gave him a 39.4 grade for the game.

The 49ers still have a lot of work to do once free agency officially begins. Again, they do need to find an edge rusher, and they do need to find a reliable wide receiver. But championships are built up front, and the 49ers do not have an interior line that is worthy of a title.

Lynch and Shanahan need to find a guard who can play a pivotal role in the ground and air attacks.

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